title: Fluctuating temperature leads to evolution of thermal generalism and preadaptation to novel environments.
abstract: Environmental fluctuations can select for generalism, which is also hypothesized to increase organisms' ability to invade novel environments. Here, we show that across a range of temperatures, opportunistic bacterial pathogen Serratia marcescens that evolved in fluctuating temperature (daily variation between 24°C and 38°C, mean 31°C) outperforms the strains that evolved in constant temperature (31°C). The growth advantage was also evident in novel environments in the presence of parasitic viruses and predatory protozoans, but less clear in the presence of stressful chemicals. Adaptation to fluctuating temperature also led to reduced virulence in Drosophila melanogaster host, which suggests that generalism can still be costly in terms of reduced fitness in other ecological contexts. While supporting the hypothesis that evolution of generalism is coupled with tolerance to several novel environments, our results also suggest that thermal fluctuations driven by the climate change could affect both species' invasiveness and virulence.
authors.affiliation: Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, Jyväskylä, FI-40014, Finland. tketola@jyu.fi.
authors.forename: Tarmo
authors.initials: T
authors.lastname: Ketola
authors.forename: Lauri
authors.initials: L
authors.lastname: Mikonranta
authors.forename: Ji
authors.initials: J
authors.lastname: Zhang
authors.forename: Kati
authors.initials: K
authors.lastname: Saarinen
authors.forename: Anni-Maria
authors.initials: AM
authors.lastname: Ormälä
authors.forename: Ville-Petri
authors.initials: VP
authors.lastname: Friman
authors.forename: Johanna
authors.initials: J
authors.lastname: Mappes
authors.forename: Jouni
authors.initials: J
authors.lastname: Laakso
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D005075:Biological Evolution; D057231:Climate Change; D004331:Drosophila melanogaster / Q000382:microbiology*; D012706:Serratia marcescens / Q000235:genetics* / Q000254:growth & development* / Q000472:pathogenicity*; D013696:Temperature; D014774:Virulence
keywords: Bacteriophage; Drosophila melanogaster; PPV; Serratia marcescens; Tetrahymena thermophila; host; invasion; oxidative stress; predation; virulence; virus